The authors used Thoratec left ventricular assist devices (VADs) for more than 30 days in eight patients. There were five left atrial (LA) (total, 513 days; range, 33-202 days) and three left ventricular (LV) cannulations (total, 484 days; range, 44-247 days). The flow provided by LA cannulation was less than that provided by LV cannulation. However, serial measurements of hematologic, renal, and hepatic function were similar for patients with LA and those with LV cannulation throughout support. Plasma free hemoglobin and lactate dehydrogenase (LDH) levels were similar for LA and LV patients. The five LA patients had one transient ischemic attack, one reversible ischemic neurologic deficit, and one stroke. The LV patients had no neurologic events (p = 0.20; LA versus LV total neurologic events). One LA patient and one LV patient died during support. Three LA patients underwent transplant, and one LA patient recovered native cardiac function. Two LV patients underwent transplant. In certain situations (e.g., recent anterior myocardial infarction; small left ventricular dimensions) LA cannulation may be advantageous. Neurologic events may be more common in LA patients, but in our small group this difference could be attributable to chance alone. LA or LV cannulation for a Thoratec VAD can provide adequate circulatory support for more than 30 days.